Biology subjects

Tellez, K.

Publications and source records attributed to Tellez, K..

4 recordsLinked to original sources

bioRxiv2022

Diverse logics and grammar encode notochord enhancers

The notochord is a key structure during chordate development. We have previously identified several enhancers regulated by Zic and ETS that encode notochord activity within the marine chordate Ciona robusta (Ciona). To better understand the role of Zic and ETS within notochord enhancers, we tested 90 genomic elements containing Zic and ETS sites for expression in developing Ciona embryos using a whole-embryo, massively parallel reporter assay. We discovered that 39/90 of the elements were active in developing embryos; however only 10% were active within the notochord, indicating that more than just Zic and ETS sites are required for notochord expression. Further analysis revealed notochord enhancers were regulated by three groups of factors: (1) Zic and ETS, (2) Zic, ETS and Brachyury (Bra), and (3) Zic, ETS, Bra and FoxA. One of these notochord enhancers, regulated by Zic and ETS, is located upstream of laminin alpha, a gene critical for notochord development in both Ciona and vertebrates. Reversing the ETS sites in this enhancer greatly diminish expression, indicating that enhancer grammar is critical for enhancer activity. Strikingly, we find clusters of Zic and ETS binding sites within the introns of mouse and human laminin alpha 1 with conserved enhancer grammar. Our analysis also identified two notochord enhancers regulated by Zic, ETS, FoxA and Bra binding sites: the Bra Shadow (BraS) enhancer located in close proximity to Bra, and an enhancer located near the gene Lrig. Randomizing the BraS enhancer demonstrates that although the Zic and ETS sites are necessary for enhancer activity, they are not sufficient. We find that FoxA and Bra sites contribute to BraS enhancer activity. Zic, ETS, FoxA and Bra binding sites occur within the Ciona Bra434 enhancer and vertebrate notochord Brachyury enhancers, suggesting a conserved regulatory logic. Collectively, this study deepens our understanding of how enhancers encode notochord expression, illustrates the importance of enhancer grammar, and hints at the conservation of enhancer logic and grammar across chordates.

developmental biology↗

bioRxiv2022

Single-cell Transcriptome and Accessible Chromatin Dynamics During Endocrine Pancreas Development

Delineating gene regulatory networks that orchestrate cell-type specification is an ongoing challenge for developmental biology studies. Single-cell analyses offer opportunities to address these challenges and accelerate discovery of rare cell lineage relationships and mechanisms underlying hierarchical lineage decisions. Here, we describe the molecular analysis of pancreatic endocrine cell differentiation using single-cell gene expression, chromatin accessibility assays coupled to genetic labeling and cell sorting. We uncover transcription factor networks that delineate {beta}-, - and{delta} -cell lineages. Through genomic footprint analysis we identify transcription factor-regulatory DNA interactions governing pancreatic cell development at unprecedented resolution. Our analysis suggests that the transcription factor Neurog3 may act as a pioneer transcription factor to specify the pancreatic endocrine lineage. These findings could improve protocols to generate replacement endocrine cells from renewable sources, like stem cells, for diabetes therapy.

developmental biology↗

bioRxiv2019

In vivo studies of glucagon secretion by human islets transplanted in mice

Relatively little is known about regulated glucagon secretion by human islet cells compared to insulin secretion from {beta} cells, despite conclusive evidence of dysfunction in both cell types in diabetes mellitus. Distinct insulin sequences in humans and mice permit in vivo studies of {beta} cell regulation after human islet transplantation in immunocompromised mice, whereas identical glucagon sequences prevent analogous in vivo measures of glucagon output from human cells. We used CRISPR/Cas9 genome editing to remove glucagon-encoding codons 2-29 in immunocompromised (NSG) mice, preserving production of other proglucagon-derived hormones, like Glucagon-like-peptide 1. These NSG-Glucagon knockout (NSG-GKO) mice had phenotypes associated with glucagon signaling deficits, including hypoglycemia, hyperaminoacidemia, hypoinsulinemia, and islet cell hyperplasia. NSG-GKO host metabolic and islet phenotypes reverted after human islet transplantation, and human islets retained regulated glucagon and insulin secretion. NSG-GKO mice provide an unprecedented resource to investigate unique, species-specific human cell regulation in vivo.

physiology↗

bioRxiv2019

Molecular and genetic regulation of pig pancreatic islet cell development

Reliance on rodents for understanding pancreatic genetics, development and islet function could limit progress in developing interventions for human diseases like diabetes mellitus. Similarities of pancreas morphology and function suggest that porcine and human pancreas developmental biology may have useful homologies. However, little is known about pig pancreas development. To fill this knowledge gap, we investigated fetal and neonatal pig pancreas at multiple, crucial developmental stages using modern experimental approaches. Purification of islet {beta}-, - and {delta}-cells followed by transcriptome analysis (RNA-Seq) and immunohistology identified cell- and stage-specific regulation, and revealed that pig and human islet cells share characteristic features not observed in mice. Morphometric analysis also revealed endocrine cell allocation and architectural similarities between pig and human islets. Our analysis unveiled scores of signaling pathways linked to native islet {beta}-cell functional maturation, including evidence of fetal -cell GLP-1 production and signaling to {beta}-cells. Thus, the findings and resources detailed here show how pig pancreatic islet studies complement other systems for understanding the developmental programs that generate functional islet cells, and that are relevant to human pancreatic diseases. Summary StatementThis study reveals transcriptional, signaling and cellular programs governing pig pancreatic islet development, including striking similarities to human islet ontogeny, providing a novel resource for advancing human islet replacement strategies.

developmental biology↗